Therapeutic treatment with many orally administered pharmaceutical compounds and mixtures thereof require a patient to take successive dosages of the compounds every four hours. The requirement of such dosage regimens is a function of normal body metabolism of the active ingredients in pharmaceutical compounds. For example treatment with ibuprofen over a long period of time, e.g., over 12 hours, requires a patient to typically take one 200 mg. tablet or caplet, another four hours later, and a third four hours after that. In doing so, the levels of the ibuprofen in blood plasma will reach peak levels shortly after the ibuprofen tablets are taken, and then the plasma levels will decrease fairly rapidly. It is desirable to reduce the number of peaks and valleys to have a more uniform rate of release of orally administered pharmaceuticals into the blood plasma leading to more uniform or constant concentrations of pharmaceutical active in the plasma. Using the present invention, for example, a single 600 mg. active tablet or caplet can be formulated which has a sustained rate of release of active resulting in much more even plasma levels over twelve (12) hours, as contrasted to three (3) 200 mg. tablets or caplets. In addition, the quantity (amount) of the matrix can be adjusted up or down to produce tablets for sustained release that have more than or less than 600 mg. of pharmaceutical active. For example, a tablet with a sustained release analagous to the 600 mg. tablet but containing 800 mg. of pharmaceutical active can be manufactured from the same matrix composition by simply increasing the size and weight of the final tablet by a multiple of 4/3.
The present invention can be utilized to obtain sustained release pharmaceutical active tablets of many different time dosages, e.g., an 800 mg. sustained release tablet which results in desired blood plasma levels over twelve (12) hours, or a 400 mg. tablets with a similar blood plasma level over a shorter time period, e.g. six (6) hours. From a practical standpoint twelve (12) hours might be the most desired interval because of normal rates of metabolism and sleeping cycles of patients.
The matrix of the present invention can be utilized to make sustained release pharmaceutical preparations in compressed tablet form. The matrix materials used are compressed into a shaped tablet form. The term "tablet" as used herein includes tablets of any shape, and includes caplets, which are tablets having a capsule shape.
Some controlled release formulations for tablets are known. Dunn et al. U.S. Pat. No. 4,308,251 (see, Example 38) discloses ibuprofen controlled-release tablets containing in carefully controlled amounts, both an erosion-promoter agent, specifically, corn starch, and a release-controlling agent, specifically, cellulose acetate phthalate. The process disclosed is to intimately mix the ibuprofen with corn starch, and to add this mixture to a solution of ethanol and methylene chloride containing cellulose acetate phthalate to form granules, which are dried, blended with colloidal silicon dioxide, and compressed into tablets. The Dunn et al. patent suggests at column 5 that (1) while the preferred release controlling agent is cellulose acetate phthalate, various other suitable agents may be used, including ethyl cellulose, and (2) while the preferred erosion-promoting agent is corn starch, various other suitable agents may be used including various vegetable starches, cellulose derivatives and cross-linked polyvinylpyrrolidone. The instant invention utilizes similar alternative ingredients but in a different manner. In the instant invention the ethyl cellulose is mixed with ibuprofen as a dry powder while a non-crosslinked PVP, which is a completely different material with different properties than the cross-linked Dunn, et al. material, is dissolved in alcohol, which is also not taught by Dunn et al. Further, different proportions of ingredients are used to make a different type of controlled-release tablet than Dunn et al.
Bhutani U.S. Pat. No. 4,684,516 discloses sustained release pharmaceutical tablets prepared by compressing together an agglomeration of distinct sets of time release coated active particles. For example, active particles are broken up into three distinct sets and each set is coated with a prescribed amount of time release coating material to provide three separate release times for the active materials. The three sets of coated particles are then pressed together in a single pill to provide a timed interval release effect for the active material. The Bhutani "agglomeration" does not provide a gradual and consistent sustained release of active but rather a jagged release of active over a set amount of intervals. Further, the Bhutani type method of separately coating particles is cumbersone and expensive and provides pills of high bulk with unfavorably low drug/inactive-excipient ratios.
Ethylcellulose is often used as a coating for particles or in combination with another polymer. Ethylcellulose and PVP have even been used together in food supplements, e.g., German Offenlegusgsschrift DE 3331262Al, published Mar. 1, 1984, discloses amino acid food supplement coated with PVP and ethylcellulose. The PVP and ethylcellulose coating thereon acts as a barrier against release and digestion of the food supplement in certain parts of the gastrointestinal tract and assures release at a later time in a targeted area of the gastrointestinal tract. This product does not provide a gradual and consistent release of food materials but rather a delayed and contemporaneous release of food materials at a desired place in the body.
It is therefore an object of the present invention to provide a novel process and matrix for sustained gradual and consistent release of pharmaceutical actives in a low bulk homogeneous form.